Mobile satellite modem for combined geostationary, medium and low earth orbit satellite operation

ABSTRACT

The present teachings include a method and computing apparatus for triggering synchronization of a satellite modem to a carrier frequency of a beam of a satellite, retrieving ephemeris information for the satellite and beam configuration information for the beam, calculating a velocity of the satellite per the ephemeris information, and adjusting the carrier frequency of the satellite modem when communicating via the beam to compensate for a doppler offset induced in the carrier frequency by the velocity. In the method, the satellite has a satellite type selected from a Geosynchronous Earth Orbit (GEO), Medium Earth Orbit (MEO) or Low Earth Orbit (LEO) type of satellite, and the satellite type is different than a satellite type of an immediately preceding synchronization.

CROSS-REFERENCE TO RELATED APPLICATIONS AND INCORPORATION BY REFERENCE

The present application is a continuation of U.S. Non-Provisionalapplication Ser. No. 17/136,558, filed Dec. 29, 2020, which isincorporated herein by reference in its entirety.

FIELD

The present teachings disclose a modem that can perform beam selectionand handover across coverage served by one or more GeostationaryEarth-Orbit (GEO) satellites, an overlapping constellation of MediumEarth-Orbit (MEO) satellites, an overlapping constellation of LowEarth-Orbit (LEO) satellites or a combination thereof. The modemmaintains proper operation with each satellite type based on a relativemotion between the modem and the satellites.

BACKGROUND

Current satellite communication systems use modems specific to thesatellite type being used. A modem, and the modem's associated groundsegment, are dedicated to a particular type of satellite operation,i.e., GEO, MEO or LEO. Access to more than one kind of satellite networkneeds two or more satellite modems, and an ability to switch betweenthem as a user terminal (UT) moves between the different types ofcoverage. This has a number of disadvantages. For example, usingmultiple modems means increased space, power, weight, and thermalimpacts on the platforms, especially in an aero environment. Moreover,performance enhancement features such as TCP/IP acceleration aretypically handled in the modem. If more than one modem type is used,then handover between modems will not be able to maintain end-to-endTCP/IP connections. This has a negative impact on the user experience asthe mobile platform switches between networks.

BRIEF SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that is further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter.

A same satellite modem operates with Geostationary Earth-Orbit (GEO),Medium Earth-Orbit (MEO) and Low Earth-Orbit (LEO) satellites. Thesatellite modem has adaptations to maintain proper operation with eachsatellite type based on the motion of the modem, or the satellite, orboth. For example, when operating with a LEO, MEO or GEO satellite, themodem uses adaptations for handling power, frequency, and timingvariations that occur due to motion of the modem. However, whenoperating with a MEO or LEO satellite, the modem uses adaptations forhandling power, frequency, and timing variations that occur due tomotion of both the satellites and the modem. In some embodiments, astationary mobility modem may use the present teachings to account for amotion of the satellites.

A system of one or more computers can be configured to performparticular operations or actions by virtue of having software, firmware,hardware, or a combination of them installed on the system that inoperation causes or cause the system to perform a method. In one aspect,the method includes triggering synchronization of a satellite modem to acarrier frequency of a beam of a satellite, retrieving ephemerisinformation for the satellite and beam configuration information for thebeam, calculating a velocity of the satellite per the ephemerisinformation, and adjusting the carrier frequency of the satellite modemwhen communicating via the beam to compensate for a doppler offsetinduced in the carrier frequency by the velocity. In the method, thesatellite has a satellite type selected from a Geosynchronous EarthOrbit (GEO), Medium Earth Orbit (MEO) or Low Earth Orbit (LEO) type ofsatellite, and the satellite type is different than a satellite type ofan immediately preceding synchronization.

In some embodiments, the method may include one or more of thefollowing. The method may include synchronizing a timing of thecommunicating via the satellite modem to a gateway. The method mayinclude synchronizing a transmit power of the transmitting from thesatellite modem. The method where the adjusting further compensates fora UT movement induced doppler offset in the carrier frequency. Themethod where the adjusting further compensates for a velocity of thesatellite relative to a gateway. The method may include directing anantenna controller to point an antenna to a real-time location of thesatellite. The method may include repointing to a new satellite having asame satellite type as the satellite type. The method where thetriggering includes one or more of receiving a message to synchronize,determining that the satellite modem is within a coverage area of thesatellite, imminent arrival of the satellite modem into the coveragearea of the satellite, and imminent departure of the satellite modemfrom a current coverage area. The method where the retrieving includesaccessing an ephemeris repository via a satellite link to retrieve theephemeris information. The method where the communicating includesreceiving and transmitting. Other technical features may be readilyapparent to one skilled in the art from the following figures,descriptions, and claims.

In one aspect, a computing apparatus includes a processor. The computingapparatus also includes a memory storing instructions that, whenexecuted by the processor, configure the apparatus to triggersynchronization of a satellite modem to a carrier frequency of a beam ofa satellite, retrieve ephemeris information for the satellite and beamconfiguration information for the beam, calculate a velocity of thesatellite per the ephemeris information, and adjust the carrierfrequency of the satellite modem when communicating via the beam tocompensate for a doppler offset induced in the carrier frequency by thevelocity, where the satellite has a satellite type selected from aGeosynchronous Earth Orbit (GEO), Medium Earth Orbit (MEO) or Low EarthOrbit (LEO) type of satellite, and the satellite type is different thana satellite type of an immediately preceding synchronization.

Additional features will be set forth in the description that follows,and in part will be apparent from the description, or may be learned bypractice of what is described.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features may be obtained, a more particular descriptionis provided below and will be rendered by reference to specificembodiments thereof which are illustrated in the appended drawings.Understanding that these drawings depict only typical embodiments andare not, therefore, to be limiting of its scope, implementations will bedescribed and explained with additional specificity and detail with theaccompanying drawings.

FIG. 1 illustrates an aspect of the subject matter in accordance withone embodiment.

FIG. 2 illustrates a method for connecting a modem to various satellitetypes according to various embodiments.

FIG. 3 illustrates an aspect of the subject matter in accordance withone embodiment.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The present teachings may be a system, a method, and/or a computerprogram product at any possible technical detail level of integration.The computer program product may include a computer readable storagemedium (or media) having computer readable program instructions thereonfor causing a processor to carry out aspects of the present invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as SMALLTALK, C++ or the like, andconventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

Reference in the specification to “one embodiment” or “an embodiment” ofthe present invention, as well as other variations thereof, means that afeature, structure, characteristic, and so forth described in connectionwith the embodiment is included in at least one embodiment of thepresent invention. Thus, the appearances of the phrase “in oneembodiment” or “in an embodiment”, as well any other variations,appearing in various places throughout the specification are notnecessarily all referring to the same embodiment.

Introduction

Providing GEO, MEO and LEO access to a stationery or moving platform,such as an aircraft, boat, or land-based vehicle, has a number ofadvantages. Coverage for a UT can be extended from a GEO network to aMEO or LEO network to provide communications access in areas beyond thereach of standard GEO networks. GEO networks are typically focused onproviding land-based communications, and therefore do not typicallyprovide coverage over water. Further, as GEO satellites are equatoriallybased, they do not provide good land or water coverage in highlatitudes, in other words, near the poles. LEO and MEO constellationstypically provide the same type of coverage over water as over land, andsome of the constellations provide good quality polar coverage.

Mobile terminals tend to travel along well-defined routes, and also tendto congregate in clusters. As examples, aircraft fly along well-definedflight paths and congregate at airports, and ships travel well-definedsea lanes and congregate at ports. This creates high demand forsatellite bandwidth in those areas. A UT that can access varioussatellite coverages allows a network operator to augment capacity invery specific areas, regardless of whether the primary access for aterminal is via a GEO, MEO or LEO constellation. For instance, a serviceprovider could use a GEO satellite with wide area coverage of NorthAmerica, and then augment this with MEO coverage around particularlybusy airports such as those in Chicago, Atlanta, and Los Angeles.Conversely a maritime provider could provide over the water coverageusing a MEO constellation, and then augment this with GEO coverage asships enter a GEO coverage area.

The present teachings reduce power, thermal, and weight requirementscompared to a multi-modem solution. In some embodiments, the presentteachings provide seamless switching, including maintenance ofend-to-end TCP/IP connections when moving between satellite networks. Acommon gateway infrastructure may be used for the LEO, MEO and GEOnetworks based on the use of a single modem type on a platform, forexample, a mobile platform.

The present teachings use the same satellite modem to operate with GEO,MEO and LEO satellites. The satellite modem has adaptations to maintainproper operation with each satellite type based on the motion of themodem, or the satellite, or both. For example, when operating with a GEOsatellite, the modem uses adaptations for handling power, frequency, andtiming variations that occur due to motion of the modem. However, whenoperating with a MEO or LEO satellite, the modem uses adaptations forhandling power, frequency, and timing variations that occur due tomotion of both the satellites and the modem. In some embodiments, astationary mobility modem may use the present teachings to account for amotion of the satellites.

In LEO and MEO operation, the size of the variations in timing andfrequency can be much larger than in GEO operation. The modem handlesthese additional variations with no change in hardware, software, orfirmware required as the modem transitions between GEO, MEO and LEOmodes. In some embodiments, the modem performs satellite and beam switchoperations in a short duration regardless of which type of satellitesare involved. The short duration may be less than 30 seconds, less than20 seconds, less than 10 seconds, less than 5 seconds, less than 2seconds or the like. The transition duration does not include antennarelated delays such as a physical antenna repoint, local oscillatorupdate, or the like. In some embodiments, end-to-end TCP/IP sessions canbe maintained by connectivity via a common data center to minimizedisruptions to user traffic during modem transitions.

Additionally, the modem may include beam selection. For example,satellite beam selection may be based on a modem's geolocation, and arelative direction and rate of travel between the modem and thesatellite. The transitioning from one beam to another may be performedwhile the modem is moving. In some embodiments, the modem may considerbeam movement across the surface of the earth due to the motion of thesatellite (for example, MEO or LEO satellites) affecting the modemposition within a beam. In some embodiments, the modem may consider theneed to switch satellites as each satellite in the constellation passesover.

In some embodiments, the modem may receive LEO or MEO ephemerisinformation. In some embodiments, ephemeris information may be broadcastover the satellite constellations. In some embodiments, an ephemerisdata server may be accessed over a satellite when coverage from thesatellite is available. In other embodiments, ephemeris information maybe provided by equipment connected locally to the modem via a LAN orother physical interface, whether pushed by the local equipment orpulled by the modem. In some embodiments, modem may be provisioned withsome ephemeris data.

The modem may be provided beam configuration information to define thecharacteristics of all satellite beams in the coverage area. The beamconfiguration information may include geographical boundaries, satellitetype (GEO/MEO/LEO), outroute carrier information, inroute carrierinformation and the like. For GEO beams, the beam configurationinformation may include satellite coordinates in the GEO arc. For MEObeams the beam configuration information may include adjustments basedon a Satellite local oscillator (LO) in the return direction and agateway (GW) geolocation. In some embodiments, the position of the beamson the earth's surface may be fixed. The beam configuration informationmay be provided in a file or the like.

The modem can perform functions appropriate to GEO or MEO type based onthe beam configuration information. For each beam type the modemcalculates the doppler offset induced in the modem's transmit carrierdue to the movement of the UT. For GEO beam types the modem then appliesa corresponding offset in the opposite direction to the transmit carriergenerated by the modem so that the carrier leaves the vehicle at thecorrect frequency.

For MEO and LEO beams, the modem also calculates Doppler induced due toa motion of the satellite. The modem processes satellite ephemeris datato compute in real time the specific satellite ID that is putting up thebeam, as well as the satellite's coordinates. The Modem uses ownlocation, satellite location and GW location to compute relativevelocity of two links in the return direction, between the Modem and theSatellite and between the Satellite and the GW. The modem uses SatelliteLO to compute Satellite to GW link's frequency from its own return linkfrequency in use. The modem computes Doppler for each of these links,adds in the Doppler shift due to the vehicle motion and shifts its Txcarrier frequency to compensate for the total Doppler experienced fromModem to GW.

The Modem directs the Antenna Controller when it is in a LEO/MEO beamand provides real time satellite location for the Antenna Controller topoint an antenna to the satellite. When a switch from a first LEO/MEOsatellite to a second LEO/MEO satellite is needed, the Modem sendscontrol information to the Antenna Controller to repoint while in aLEO/MEO beam of the first LEO/MEO satellite. After the repointing, theModem may trigger Tx link resynchronization for timing and power due tothe switch in satellites. Further, the modem accounts for Satellitespecific offset to the base LO in the return direction. In someembodiments, switching time between satellites maybe minimized by usinga make-before-break scheme (obtain lock with new satellite prior tobreaking lock with old satellite), by for example, using multipledirectional antennas with the antenna controller.

FIG. 1 illustrates an exemplary satellite network according to variousembodiments.

The Satellite network 100 includes a coverage area 102, GWs 112 a, asatellite s1 116 a, a UT 118, a Terrestrial Network 120 and an ISP 114(internet service point). The GWs 112 a can service a s1 cell 104 a, as1 cell 104 b, a s1 cell 104 c with s1 beams 106. Different s1 beams 106may be served by different GWs 112 a. When the UT 118 is disposed in orimminently arriving in an overlap 122 of two or more cells, for examples1 cell 104 a and s1 cell 104 b, a beam switch between respective beamsof the service areas may be initiated. A beam switch between serviceareas of a common satellite may need a switch of gateways also.

The coverage area 102 may also be served a satellite s2 116 b servicinga s2 cell 108 a and a s2 cell 108 b with s2 beams 110 using GWs 112 b.GWs 112 a and GWs 112 b may be connected via the Terrestrial Network120. The overlap 122 may be between a s1 cell and an s2 cell, forexample, s1 cell 104 a and s2 cell 108 b. In such an overlap, the beamswitch may switch satellites that needs a switch of gateways also. TheGWs 112 a and GWs 112 b may provide UTs 118 with internet access via theISP 114. The satellite s1 116 a and satellite s2 116 b may be ofdifferent satellite types, for example, GEO, LEO or MEO.

FIG. 2 illustrates a method for connecting a modem to various satellitetypes according to various embodiments.

In operation 202, method 200 retrieves ephemeris information for thesatellite and beam configuration information for the beam. In operation204, method 200 triggers synchronization of a satellite modem to acarrier frequency of a beam of a satellite. In operation 206, method 200calculates a velocity of the satellite per the ephemeris information. Inoperation 208, method 200 adjusts the carrier frequency of the satellitemodem when communicating via the beam to compensate for a doppler offsetinduced in the carrier frequency by the velocity. In method 200 thesatellite has a satellite type selected from a Geosynchronous EarthOrbit (GEO), Medium Earth Orbit (MEO) or Low Earth Orbit (LEO) type ofsatellite, and the satellite type is different than a satellite type ofan immediately preceding synchronization.

In operation 210, method 200 directs an antenna controller to point anantenna to a real-time location of the satellite. In operation 212,method 200 synchronizes a timing of the communicating via the satellitemodem to a gateway. In operation 214, method 200 synchronizes a transmitpower of the transmitting from the satellite modem.

FIG. 3 illustrates an aspect of the subject matter in accordance withone embodiment.

The system 300 includes various modules including a Trigger SatelliteChange 302, a Select New Satellite 304, an Ephemeris info 306, anEphemeris data 308, a Direct Antenna Controller 310, an Adjust CarrierFrequency 312, an Adjust power 314, an Adjust Timing 316, and aCalculate Velocities 318 module.

An external or internal event to the system 300 may invoke TriggerSatellite Change 302 due to an impending arrival into or departure froma coverage area, for example. Trigger Satellite Change 302 thenestablishes a beam lock (inroute or outroute) with Select New Satellite304. Select New Satellite 304 uses Ephemeris info 306 and Ephemeris data308 to Direct Antenna Controller 310 to aim at the selected newsatellite. Once Direct Antenna Controller 310 operation is complete,Adjust Carrier Frequency 312, Adjust Timing 316 and Adjust power 314operations can be performed. Adjust Carrier Frequency 312 uses CalculateVelocities 318 to calculate one or more of a UT velocity, a selected newsatellite velocity and a relative velocity between the UT and theselected new satellite.

Having described preferred embodiments of a system and method (which areintended to be illustrative and not limiting), it is noted thatmodifications and variations can be made by persons skilled in the artconsidering the above teachings. It is therefore to be understood thatchanges may be made in the embodiments disclosed which are within thescope of the invention as outlined by the appended claims. Having thusdescribed aspects of the invention, with the details and particularityrequired by the patent laws, what is claimed and desired protected byLetters Patent is set forth in the appended claims.

What is claimed is:
 1. A method comprising: triggering synchronizationof a satellite modem to a carrier frequency of a beam of a satellite;retrieving an ephemeris information for the satellite and a beamconfiguration information for the beam; calculating a velocity of thesatellite per the ephemeris information; and adjusting a carrierfrequency of the satellite modem when communicating via the beam tocompensate for a doppler offset induced in the carrier frequency by thevelocity, wherein the satellite modem is capable of communicating with aGeosynchronous Earth Orbit (GEO), Medium Earth Orbit (MEO) and Low EarthOrbit (LEO) type of satellite.
 2. The method of claim 1, furthercomprising synchronizing a timing of the communicating via the satellitemodem to a gateway.
 3. The method of claim 1, further comprisingsynchronizing a transmit power of the transmitting from the satellitemodem.
 4. The method of claim 1, wherein the adjusting furthercompensates for a UT movement induced doppler offset in the carrierfrequency.
 5. The method of claim 1, wherein the adjusting furthercompensates for a velocity of the satellite relative to a gateway. 6.The method of claim 1, further comprising directing an antennacontroller to point an antenna to a real-time location of the satellite.7. The method of claim 1, further comprising repointing to a newsatellite having a same satellite type as the satellite type.
 8. Themethod of claim 1, wherein the triggering comprises one or more ofreceiving a message to synchronize, determining that the satellite modemis within a coverage area of the satellite, imminent arrival of thesatellite modem into the coverage area of the satellite, and imminentdeparture of the satellite modem from a current coverage area.
 9. Themethod of claim 1, wherein the retrieving comprises accessing anephemeris repository via a satellite link to retrieve the ephemerisinformation.
 10. The method of claim 1, wherein the communicatingcomprises receiving and transmitting.
 11. A computing apparatuscomprising: a processor; and a memory storing instructions that, whenexecuted by the processor, configure the apparatus to: triggersynchronization of a satellite modem to a carrier frequency of a beam ofa satellite; retrieve an ephemeris information for the satellite and abeam configuration information for the beam; calculate a velocity of thesatellite per the ephemeris information; and adjust a carrier frequencyof the satellite modem when communicating via the beam to compensate fora doppler offset induced in the carrier frequency by the velocity,wherein the satellite modem is capable of communicating with aGeosynchronous Earth Orbit (GEO), Medium Earth Orbit (MEO) and Low EarthOrbit (LEO) type of satellite.
 12. The computing apparatus of claim 11,wherein the instructions further configure the apparatus to synchronizea timing of the communicating via the satellite modem to a gateway. 13.The computing apparatus of claim 11, wherein the instructions furtherconfigure the apparatus to synchronize a transmit power of thetransmitting from the satellite modem.
 14. The computing apparatus ofclaim 11, wherein the adjusting further compensates for a UT movementinduced doppler offset in the carrier frequency.
 15. The computingapparatus of claim 11, wherein the adjusting further compensates for avelocity of the satellite relative to a gateway.
 16. The computingapparatus of claim 11, wherein the instructions further configure theapparatus to direct an antenna controller to point an antenna to areal-time location of the satellite.
 17. The computing apparatus ofclaim 11, wherein the instructions further configure the apparatus torepoint to a new satellite having a same satellite type as the satellitetype.
 18. The computing apparatus of claim 11, wherein the triggeringcomprises one or more of receiving a message to synchronize, determinethat the satellite modem is within a coverage area of the satellite,imminent arrival of the satellite modem into the coverage area of thesatellite, and imminent departure of the satellite modem from a currentcoverage area.
 19. The computing apparatus of claim 11, wherein theretrieving comprises access an ephemeris repository via a satellite linkto retrieve the ephemeris information.
 20. The computing apparatus ofclaim 11, wherein the communicating comprises receive and transmitting.